安装Oracle 11g RAC时，我们需要配置ntp服务。在使用虚拟机的情况下对于时钟同步方式的配置有很多种方式，可以使用vmware自带的时钟同步功能，也可以直接将本地的一个节点用作时间服务器。本文介绍直接配置ntp方式的时钟服务器。
1、查看两节点的hosts配置
[root@node1 ~]# cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
#127.0.0.1 localhost.localdomain localhost
#::1 localhost6.localdomain6 localhost6
127.0.0.1 localhost.szdb.com localhost
# Public eth0
192.168.7.71 node1.szdb.com node1
192.168.7.72 node2.szdb.com node2
#Private eth1
10.10.7.71 node1-priv.szdb.com node1-priv
10.10.7.72 node2-priv.szdb.com node2-priv
#Virtual
192.168.7.81 node1-vip.szdb.com node1-vip
192.168.7.82 node2-vip.szdb.com node2-vip
2、确认各节点的ntp包已经安装
[oracle@node1 ~]$ rpm -qa | grep ntp
ntp-4.2.2p1-9.el5_4.1
chkfontpath-1.10.1-1.1 #这个是和字体有关，非ntp包
[oracle@node1 ~]$ ssh node2 rpm -qa | grep ntp
ntp-4.2.2p1-9.el5_4.1
chkfontpath-1.10.1-1.1 #这个是和字体有关，非ntp包
3、编辑两节点的ntp.conf文件
[oracle@node1 ~]$ su - root
Password:
[root@node1 ~]# vi /etc/ntp.conf
#New ntp server added by Robinson
server 127.127.1.0 prefer # 添加首选的时钟服务器
restrict 192.168.7.0 mask 255.255.255.255 nomodify notrap #只允许192.168.7.*网段的客户机进行时间同步
broadcastdelay 0.008
[root@node2 ~]# vi /etc/ntp.conf
#New ntp server added by Robinson
server 192.168.7.71 prefer
broadcastdelay 0.008
4、编辑两节点的ntpd参数
[root@node1 ~]# vi /etc/sysconfig/ntpd
#The following item added by Robinson
#Set to 'yes' to sycn hw clock after successful ntpdate
SYNC_HWCLOCK=yes #此选项用于自动校准系统时钟与硬件时钟
OPTIONS="-x -u ntp:ntp -p /var/run/ntpd.pid"
#注意理解Linux的时钟类型。在Linux系统中分为系统时钟和硬件时钟.
#系统时钟指当前Linux kernel中的时钟，而硬件时钟指的是BIOS时钟，由主板电池供电的那个时钟
#当Linux启动时，硬件时钟会读取系统时钟的设置，之后系统时钟就独立于硬件时钟运作
[root@node2 ~]# vi /etc/sysconfig/ntpd
The following item added by Robinson
SYNC_HWCLOCK=yes
OPTIONS="-x -u ntp:ntp -p /var/run/ntpd.pid"
5、配置ntp自启动服务
[root@node1 ~]# chkconfig ntpd on
[root@node2 ~]# chkconfig ntpd on
6、在两节点启动ntp服务
[root@node1 ~]# service ntpd stop
Shutting down ntpd: [FAILED]
[root@node1 ~]# service ntpd start
ntpd: Synchronizing with time server: [FAILED]
Starting ntpd: [ OK ]
[root@node2 ~]# service ntpd restart
Shutting down ntpd: [ OK ]
ntpd: Synchronizing with time server: [ OK ]
Syncing hardware clock to system time [ OK ]
Starting ntpd: [ OK ]
7、查看ntp状态
[root@node1 ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
LOCAL(0) .LOCL. 10 l 40 64 1 0.000 0.000 0.001
[root@node2 ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
node1.szdb.com .INIT. 16 u 60 64 0 0.000 0.000 0.000
LOCAL(0) .LOCL. 10 l 59 64 1 0.000 0.000 0.001
#Author : Robinson
#Blog: http://blog.csdn.net/robinson_0612
也可以使用watch ntpq -p方式查看实时状态
8、ntp的相关日志
[root@bigboy tmp]# cat /var/log/messages | grep ntpd